When Sophie chose to have her family's memories wiped, she requested that Alden give them a big yard so that they could get a dog. They ended up getting a beagle that her family named Watson.
Watson, along with Marty, went to Atlantis with Sophie and Amy in Nightfall. Apparently, he and Marty were quite vicious, shredding Alden's tunic sleeves.
It can be noted that Watson is the name of Sherlock Holmes' companion, a common motif in the KotLC universe.